1. Field of the Invention
The invention relates to the field of instrumentation, in particular, to measurement of micromovement, and may be used for measuring, detecting, and recording creeping and dynamic infraprocesses in nature, engineering, and bionics; for example, for recording baric, thermal, and hygrometric tendencies in meteorology; for recording creeping of engineering structures; for testing leakproofness of small and large installations and in security systems; as well as for recording seismic, infrasound, and gravitation waves. In bionics, the proposed device may be used as a part of tactile sensitivity, in bionic prostheses, bionic robots, and zoo-robots.
2. Description of the Related Art
To address the above problems, measuring systems should have maximum possible sensitivity up to Angstrom units (Å)-wide dynamic ranges and low sluggishness.
At present, the highest sensitivity and widest dynamic ranges are provided by X-ray interferometers which implement spectrometric methods of measuring. However, in the cases which lie outside metrology and investigations of crystal structure of materials, the use of X-ray interferometers does not find application owing to high sluggishness of the sensitive elements employed, cumbersome apparatus design, complexity, and high price.
Capacitive and inductive transducers have found wide application for measuring small movements. The limitation of their use is attributed to the fact that raising the sensitivity of these transducers necessarily leads to narrowing of the dynamic range because of non-linearity of their analog measuring characteristics. The section of a particular portion of the characteristics determines the dynamic range of the transducer.
Devices are known for measuring small movements that are based on artificial quantization of linear or angular movements by means of the distributed quantizing measuring elements or grids. As an example, an incremental encoder may be used. Resolution of such types of encoders depends on the number of sensitive segments on the disk or band of the transducer, which determines a mechanical limit of their sensitivity, such as no more than 0.01 microns.
The closest known device to the present invention is a micromovement sensor according to the U.S.S.R. Patent Number 947,626, in which a method of measuring using natural quantization effects is described. The micromovement sensing device contains a transducer consisting of sensitive and measuring elements which convert the monotonic movements to a pulse-delta-modulated electric signal. A sensitive element is fixed on an elastic membrane and interacts with a source of the micromovement, such as the tested object, while a spring-loaded mobile measuring element is a core of the electromagnet which fixes the measuring element in the position of contact with the sensitive element, when applying exciting current from a signal conditioner.
In the initial state, the electric contact between sensitive and measuring elements creates a closed electric circuit through which electric current flows. As a result, an exciting current appears at the output of the signal conditioner which energizes the electromagnet and fixes the measuring element. When the tested object shifts, the sensitive element moves in the direction of breaking the contact between the measuring and sensitive elements due to the action of a measuring force created by the membrane. At the instant of the breaking of the electric circuit, the signal conditioner removes the exciting current from the winding of the fixing electromagnet, and the measuring element, under the action of a spring, moves in the direction toward the sensitive element until contact between the sensitive and measuring elements is recovered and the measuring element is fixed in a new position.
The breaking and recovering of the contact forms the leading and trailing edges of the pulse signal which is equivalent to a single movement of the measuring element, thus performing conversion of monotonic movement to a pulse-delta-modulated electric signal by the use of a natural quantization effect of hysteresis. The quantized movement is characterized by the value determined by two states of the electric contact; that is, closed or broken.
The disadvantage of the known device is determined by the fact that, at the instant in which contact between the measuring and sensitive elements is set up, the force of the spring pressure moving the measuring elements is transmitted through the sensitive element onto the tested object, in which elastic microdeformation arises as a result of this contact force. The value of this microdeformation restricts the ultimate attainable sensitivity of the known device to the level of 0.2 microns. In addition, when electric contact is broken, an electroerosive bridge arises, causing a bridge current to be detected by the signal conditioner as the presence of the contact, and the measuring pulse arises only after bridge breaking. Thus, the length of every micromovement of the measuring element cannot be less than the length of the electroerosive bridge and the value of arisen microdeformation taken together. Additionally, occurrence of the electroerosive bridge leads to a geometry violation of the contact elements which causes instability of their meteorological characteristics.